Advanced Polymer Dispersion and a Capacitor on its Base

ABSTRACT

The present invention is related to a polymer dispersion comprising first conductive polymer particles having a positive Z-potential and second conductive polymer particles having a negative Z-potential, a method of forming the polymer dispersion, a method of making a capacitor comprising the polymer dispersion and a capacitor comprising the polymer dispersion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority to pending U.S. Provisional PatentApplication No. 63/249,225 filed Sep. 28, 2021 which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention is related to an improved dispersion which isparticularly suitable for use in the manufacture of an electrolyticcapacitor having improved capacitance and ESR.

BACKGROUND

Conducting polymers are widely used in solid electrolyte capacitors.High voltage and high reliability capacitors are manufactured usingconducting polymer from dispersions wherein solid phase polymerparticles are distributed in liquid phase solvent(s). The preparation ofdispersions is known specifically for use in the manufacture ofelectrolytic capacitors. The focus in the art has been primarily oneither the particle size of the polymer in the dispersion, as evidencedin U.S. Pat. No. 8,699,208 which is incorporated herein by reference, oron the final structure of the polymer layers in the capacitor, asevidenced in U.S. Pat. Nos. 10,381,167 and 10,074,490 both of which areincorporated herein by reference. The first approach has a significantbig drawback in that the particle size range is assumed to be the onlylimiting factor of capacitor anode modification but there are otherfactors not previously appreciated.

In spite of the advances, the industry continues to demand betterperformance from polymer-based capacitors. There has been a particulardemand for improved performance with regards to the compatibility offormed conductive polymers used in combination with liquid electrolytes,referred to as hybrid capacitors, at extended temperature ranges such as125-165° C. This is important for hybrid electrolytic capacitors wherethe solid-state polymer is present in the capacitor with a liquidelectrolyte at the same time. There is also a trend towardsminiaturization of electrolytic capacitors which has become more easilyobtained through the use of highly conducting polymers. Nevertheless,further advances are required to meet the demands and to achieve therequired capacitance. Thus, a high degree of coverage of the dielectriclayer on the anode surface becomes very important to achieve.

It has not been previously realized that the Z-potential of theconducting polymer can have an adverse effect on the coating quality onthe surface of the dielectric. As illustrated schematically in FIG. 1 ,conductive polymer particles of opposite charge are attracted to thesurface of the dielectric, represented in this graphic without limitthereto, as negatively charged polymer particles being attracted to thepositively charged surface. As the surface coating increases the chargeof the surface is gradually reversed which inhibits further formation ofadditional polymer particles in the coating. The subsequent polymerparticles are less likely to be adsorbed from the solution and thereforethey cannot contribute to the continued building of the coating. Upondrying forces polymer particles can be deposited with an interlaced saltlayer, with counter ions compensating for the same charge which weakensthe integrity of the coating. The result is the potential fordelamination due to affinity of the small counter ions to solvation byelectrolyte, in a hybrid capacitor, or moisture, in a solid electrolytecapacitor. Therefore, the coating quality is effectively limitedresulting in defects.

The present invention provides an improved surface coating and thereforean improved capacitor.

SUMMARY OF THE INVENTION

The present invention is related to an improved dispersion wherein theimproved dispersion provides superior coatings on a charged surface.

More specifically, the present invention is related to improvedcapacitors, particularly hybrid capacitors, wherein dispersion ofconductive polymer comprising a combination of positive Z-potentialpolymer particles and negative Z-potential polymer particles providesuperior performance.

A particular feature of the invention is the ability to form a capacitorcomprising improvements in capacitance and equivalent series resistance(ESR).

These and other embodiments, as will be realized, are provided in apolymer dispersion comprising first conductive polymer particles havinga positive Z-potential and second conductive polymer particles having anegative Z-potential.

Yet another embodiment is provided in a method for forming a polymerdispersion. The method of forming a polymer dispersion comprises:providing a conductive polymer dispersion wherein the conductive polymercomprises a conductive polymer in a bipolaron state;

-   subjecting the conductive polymer dispersion to high-pressure    homogenization thereby converting the conductive polymer into first    polymer particles having a positive Z-potential and second polymer    particles having a negative Z-potential.

Yet another embodiment is provided in a method for forming a capacitor.The method comprises:

-   forming an anode;-   forming a dielectric on the anode; and-   forming a conductive polymer layer on the dielectric by applying a    dispersion comprising first polymer particles having a positive    Z-potential and second polymer particles having a negative    Z-potential.

Yet another embodiment is provided in a capacitor comprising an anode, adielectric on the anode, and a conductive polymer layer on thedielectric wherein the conductive polymer layer comprises firstconductive polymer particles having a positive Z-potential and secondconductive polymer particles having a negative Z-potential.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 schematically illustrates coating the prior art.

FIG. 2 schematically illustrates a Z-negative polymer particle.

FIG. 3 graphically illustrates the potential distribution for a polymerparticle with positive surface charge wherein positive Z-potentialindicates absence of specific adsorption and negative Z-potentialindicates specific adsorption of anions.

FIGS. 4A-4D schematically Illustrates an embodiment of the invention.

FIG. 5 illustrates a neutral state, polar state and bipolar state of arepresentative conductive polymer.

FIG. 6 graphically illustrates surface potential as a function of pH inthe presence of different anions.

FIGS. 7A-7C graphically illustrates the invention.

FIG. 8 graphically illustrates the invention.

FIG. 9 graphically illustrates the invention.

FIG. 10 graphically illustrates the advantages of the invention.

DESCRIPTION

The present invention is related to an improved dispersion which isparticularly suitable for use in the manufacture of an electrolyticcapacitor, particularly the cathode of an electrolytic capacitor,wherein the capacitor exhibits improved capacitance and improved ESR.More specifically, the present invention is related to a dispersioncomprising first polymer particles with a positive Z-potential andsecond polymer particles with a negative Z-potential and capacitorscomprising the dispersion.

The invention will be described with reference to the figures which forman integral part of the disclosure provided for clarification withoutlimiting the invention.

A positive Z-particle is illustrated schematically in FIG. 2 . In FIG. 2, the core, 10, is a polymer particle with a negatively charged surfacehaving a surface potential, SP. Positive polymer particles, 12, areelectrostatically attracted to the surface thereby forming a coating andconverting the surface to a positively charged surface for the coatedpolymer particle. The thickness of the coated layer, as measured fromthe tangent of the core to the tangent of the positive polymerparticles, is referred to as the Stern layer, 14. Nonbound positivelycharged polymer particles, 16, are unable to contribute to the coatingdue to electrostatic repulsion thereby creating an electrical doublelayer, 18, wherein the nonbound positively charge polymer particles arein a slipping plane, 20, of the electrical double layer. The area beyondthe slipping plane is referred to as the diffuse layer. Representativepotential, in mV, as a function of distance, D, from the polymerparticle surface decreases as illustrated graphically in FIG. 2 .

FIG. 3 graphically illustrates a representative potential distributionfor a polymer particle with positive surface charge wherein positiveZ-potential indicates absence of specific adsorption and negativeZ-potential indicates specific adsorption of anionic material.

An embodiment of the invention will be described with reference to FIGS.4A-4D. In FIGS. 4A-4D an improved coating, and process for forming thecoating, is illustrated schematically. For the purposes of illustration,without limit thereto, the invention will be illustrated utilizing analuminum metal with an aluminum oxide dielectric wherein the surface ofthe dielectric is in the pH range of 1 to 8, more preferably 3 to 8, andis positively charged as illustrated schematically in FIG. 4A. During afirst modification, represented in FIG. 4B, the first layer ofconductive polymer particles, having a charge which is opposite thesurface or a negative Z-potential in this illustration, adsorb on thesurface of the dielectric. Adhesion is supported by the electrostaticforces resulting in a reversal of the effective surface charge relativeto the charge of the dielectric surface.

During a second modification, illustrated in FIG. 4C, a second layer ofconductive polymer particles, having a charge opposite to the firstlayer or conductive polymer particles or a positive Z-potential in thisillustration, are now attracted to the surface and adsorb on the surfacethereby again reversing the effective surface charge. After a sufficientnumber of polymer particles of the second layer have formed a coatingthe polymer particles having a negative Z-potential, in thisillustration, are again attracted to the surface as illustratedschematically in FIG. 4D.

As would be realized the process of alternating the effective chargesurface results in a much thicker conductive coating, and thereforefewer coating defects, thereby providing improved capacitance andreduced ESR. The entire polymer layer thickness increases with eachcycle and vacancies in the coating are significantly reduced oreliminated. The resulting polymer layer has better resistance towardsdelamination in the presence of electrolytes. The cycles can be repeatedwith drying and curing steps, if necessary, to form a uniform surface.

Dispersions comprising positive Z-potential conducting polymer particlesand negative Z-potential conducting polymer particles are formed byhigh-pressure homogenization of a dispersion comprising a conductivepolymer in a bipolaron state. Conjugated polymers demonstrate higherconductivity in the positive bipolaron state wherein the polymer isoxidized from the neutral state to the bipolar state as described in USPublished Patent Application 2022/0059296 which is incorporated hereinby reference. The polaron state is formed by chemical or electrochemicaloxidation of the neutral polymer chain with further oxidation leading tothe bipolaron state which for polythiophene, as a representativeconductive polymer, is represented schematically in FIG. 5 . In FIG. 5the top structure is neutral, the central structure is a polaron and thebottom structure is a bipolaron.

The bipolaron state corresponds to a high degree of p-doping since theFermi energy level is closer to the Highest Occupied Molecular Orbital(HOMO) energy level. For some conducting polymers a neutral chain canturn to a polaron or bipolaron through protonation, such as by treatmentwith low pH solutions, however this must be considered as anintramolecular oxidation by protons. With polyaniline (PAN) andpolypyrole (PPY) conductive polymers electrons have to be accepted fromlow energy electron levels for a proton to be involved in the reactionand therefore the concentration should thermodynamically allow theprocess of “hole” generation from the accepted proton. If a proton isnot involved, as in a dispersion comprisingpoly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonate(PSS), the polymer doping can be conducted only through intermolecularoxidation.

For the purposes of the instant disclosure high-pressure homogenizationa a process wherein the dispersion is passed through a homogenizer at ahigh pressure drop of 250 to 1000 bar.

An inventive polymer dispersion comprises conducting polymer particleshaving an average polymer particle size of at least 5 nm, morepreferably at least 10 nm and more preferably at least 50 nm. Even morepreferably the polymer particles have an average polymer particle sizeof 100-500 nm and more preferably 100-200 nm wherein polymer particlesize is the diameter of a circle having the same mass as the polymerparticle being measured. Polymer particles of this polymer dispersionhave a core and a shell. The core is charged positively vs. the shell.Polymer particles of the polymer dispersion are fractionized in at leasttwo different polymer particle types which have different surfacecomposition and different Z-potential. Both polymer particle types areoriginated from a single polymer particle type dispersion, byhigh-pressure homogenization, with average polymer particle size priorto homogenization of from 100 nm to 5000 nm. After high-pressurehomogenization the two polymer particle types having differentZ-potentials are characterized by their PSS/PEDOT surface ratio with thehigher PSS/PEDOT surface ratio representing a negative Z-potentialpolymer particle and the lower PSS/PEDOT surface ratio representing apositive Z-potential polymer particle.

Agglomeration of the positive Z-potential polymer particle and negativeZ-potential polymer particle is suppressed by dilution. At dilution of 1to 1000 polymer particle sizes are close to those measured using a CTScentrifuge. However, at dilutions lower than 1 to 50 the size is 5-6times larger due to agglomeration wherein polymer particles withpositive Z-potential get a recharged surface. Negative Z-potentialpolymer particles can be stabilized by salicylic acid adsorbed by thepolymer particles. Salicylic acid in a small concentration can eliminateor significantly suppress the agglomeration process.

Z-potential can be measured for polymer particles of the dispersionusing Dynamic Light Scattering methods. The Z-potential of positivelycharged polymer particles is preferably in the range of 10 mV to +150 mVand the Z-potential of negatively charged polymer particles is in therange of form 0 mV to −150 mV.

The difference in Z-potentials is preferably at least 20 mV when thedispersion is diluted about 500 times with deionized water. Both polymerparticle types can interact in the dispersion forming agglomerates whichare at least 4 times larger in size than the polymer particles.

An additive is optionally added to the inventive polymer dispersion toform an adjunct dispersion. The additive is specifically adsorbed inhigher degree on the surface of the polymer particles which have higherZ-potential than on surface of the polymer particles having lowerZ-potential thereby forming a modified polymer particle. Molecules orions of the additive are negatively charged and change the Z-potentialof the conducting polymer particles thereby decreasing the differencebetween Z-potential of the polymer particle types to less than 20 mV inthe adjunct dispersion. The adjunct dispersion comprises at least twodifferent polymer particle types have different surface composition butnearly equal Z-potential with difference not larger than 20 mV due tothe incorporation of the additive.

The additive is an acid or salt which preferentially ligates to apolymer particle having a positive Z-potential. Preferred additivesinclude aromatic acids or salts such as alts selected from the groupconsisting of salicylic acid, phthalic acid, benzoic acid andstyrene-4-sulfonic acid. Other preferred additives include oligo orpoly-acids or their salts such as acids selected from the groupconsisting of 2,3,4,4-tetrahydroxybutanoic acid,1,2,3,4-butanetetracarboxylic acid and polystyrene sulfonic acid.

The inventive dispersion is particularly suitable for formation of anelectrolytic capacitor comprising a polymeric cathode formed from theinventive dispersion. An electrolytic capacitor can be formed having aworking voltage up to 500 volts by applying the inventive dispersion inmultiple steps. The inventive dispersion is particularly suitable forforming capacitors having a working voltage of 35V-500V.

The adjunct dispersion, comprising an additive, is particularly suitablefor forming a polymer electrolytic capacitor with a working voltage of3V-35V. For the purposes of the invention the working voltage is definedas 80% of the break-down voltage wherein the break-down voltage is theaverage voltage that identically prepared capacitors fail.

While not limited to theory, it is hypothesized that the inventivedispersion allows the polymer particles to more effectively penetrateinto small diameter channels of the dielectric and underlying foil orpressed powder.

Surface charge of the dielectric can be altered by anions even atrelatively low pH as illustrated graphically in FIG. 6 . The presence ofanions with specific adsorption to the alumina surface is negative at pH3 and higher. In this case it is important to have Z-positive polymerparticles in the polymer dispersion which allow a good interactionbetween the polymer particles and the dielectric surface resulting in animproved surface coverage and great adhesion between the polymer and thedielectric. As would be realized the capacitor dielectric surface chargecan depend on solution pH and specific adsorption of anions or cations.

The Z-potential of representative dispersions in illustrated in FIGS.7A-7C. The scans were obtained using a Zetasizer Ultra from MalvernPanalytical.

The polymer capacitor manufacturing often requires several depositionsteps with drying and polymer curing stages in between themodifications. Modification of the dielectric can happen during a dryingprocess of applied polymer dispersion on, or in, the capacitor elementor material. During the drying stage the pH can change leading to achange of the dielectric surface potential. In this case if initiallypositively charged surface of alumina, for aluminium anode modificationat pH lower than 7, the surface charge can become negative duringmodification which will affect adhesion of the negatively charged nanopolymer particles of the polymer dispersion leading to poor surfacecoverage, lower final capacitance, higher ESR and decreased stability atdifferent conditions such as low or high temperatures, charge/discharge,etc. The inventive dispersion provides protection against alterations ofthe dielectric during drying.

The problem related to low dielectric coverage with conducting polymerand poor electrolyte compatibility of highly conducting polymers inhybrid polymer capacitors is solved by the use of a dual Z-potentialconducting polymer dispersion and a manufacturing method for polymercapacitor based on the dispersion.

The problem of poor dielectric coating and conducting polymer layerdelamination, due to thermal or electrical stress leading to capacitancedrop, in hybrid and solid polymer capacitors is also solved by the useof the inventive dual Z-potential conducting polymer dispersion andmanufacturing method for polymer capacitor based on the dispersion.

Polymer particle surfaces can be charged positively or negatively forboth Z-positive and Z-negative polymer particle types. Z-potentialtuning can be done by changing the polymer particle charge or byspecific adsorption of ionic components on the surface of the polymerparticles.

EXAMPLES Example 1

Dispersion A was prepared based on conducting polymer nanoparticlescomprising poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate(PEDOT/PSS) with oxidized core, positive core charge, and with excessiveamount of polyanion assuring specific adsorption of the anion on thesurface of the polymer particles or incorporation of the polyanions inthe polymer particle surface. Dispersion B was prepared based onconducting polymer nanoparticles of PEDOT/PSS with an oxidized core,positive core charge, and with a lower polyanion/conducting polymerratio where specific adsorption of the anion on the surface of thepolymer particles or incorporation of the polyanions in the polymerparticle surface are suppressed. Dispersion C was prepared by mixingDispersion A and dispersion B. Polymer particles of both A and B typeshave positively charged core what prevents the polymer sedimentationeven if Z-positive and Z-negative polymer particles form agglomerationswith time dispersion in the final dispersion C.

Example 2

Example 2 was the same as Example 1 except that quantities of thepolyanion are the same for Dispersion A and Dispersion B. Dispersion Awas treated with a surface-active anionic substance of a low molecularweight, with salicylic acid being exemplary, to assure negative surfacecharge. Dispersion C was prepared by mixing Dispersion A and DispersionB.

FIG. 8 graphically illustrates normalized curves for Z-positive andZ-negative polymer particles from Examples 1 and 2.

Example 3

Dispersion A was prepared based on conducting polymer nanoparticles ofPEDOT/PSS with higher degree oxidized core, higher positive charge ofthe core, and with an excessive amount of polyanion thereby assuringspecific adsorption of the anion on the surface of the polymer particlesor incorporation of the polyanions in the polymer particle surface.Dispersion B was prepared based on conducting polymer nanoparticles ofPEDOT/PSS with less oxidized core, lower positive charge of core, andthe same polyanion/conducting polymer ratio as applied for Dispersion A.Dispersion C was prepared by mixing Dispersion A and Dispersion B.Polymer particles of both A and B types have positively charged corethat prevents the polymer sedimentation even if Z-positive andZ-negative polymer particles form agglomerations with time dispersion inthe final dispersion C.

FIG. 9 graphically illustrates normalized curves for Z-positive andZ-negative polymer particles from Example 3.

Method of Preparing a Capacitor

A capacitor was produced by applying of a polymer dispersion on a porousbody of an electrode material comprising a dielectric on the surface ofthe electrode. The polymer dispersion comprised conducting polymerparticles of at least two types wherein one has a positive Z-potentialand the other one has a negative Z-potential. The polymer dispersioncomprised conducting polymer particles with average polymer particlesize, calculated as average based on number of polymer particles, atleast 0.010 micro meters or larger but not larger than 0.5 micro meter.

A 6.3V working voltage capacitors was prepared using an inventivedispersion with salicylic acid. The capacitance yield and ESR showedsignificant as illustrated graphically in FIG. 10 .

The invention has been described with reference to the preferredembodiments without limit thereto. One of skill in the art would realizeadditional embodiments and improvements which are not specificallystated but which are within the meets and bounds of the claims appendedhereto.

Claimed is:
 1. A polymer dispersion comprising first polymer particleshaving a positive Z-potential and second polymer particles having anegative Z-potential.
 2. The polymer dispersion of claim 1 wherein saidfirst polymer particles have a charge of 10 mV to +150 mV and saidsecond polymer particles have a charge of 0 mV to −150 mV.
 3. Thepolymer dispersion of claim 1 wherein said first polymer particles andsaid second polymer particles have a charge difference of at least 20mV.
 4. The polymer dispersion of claim 1 wherein said first polymerparticles and said second polymer particles have an average particlesize of at least 5 nm.
 5. The polymer dispersion of claim 4 wherein saidfirst polymer particles and said second polymer particles have anaverage particle size of at least 10 nm.
 6. The polymer dispersion ofclaim 5 wherein said first polymer particles and said second polymerparticles have an average particle size of at least 50 nm.
 7. Thepolymer dispersion of claim 6 wherein said first polymer particles andsaid second polymer particles have an average particle size of 100-500nm.
 8. The polymer dispersion of claim 9 wherein said first polymerparticles and said second polymer particles have an average particlesize of 100-200 nm.
 9. The polymer dispersion of claim 1 furthercomprising an additive wherein said additive adheres to said firstpolymer particles thereby forming an adjunct dispersion.
 10. The polymerdispersion of claim 9 wherein said adjunct dispersion comprises modifiedfirst polymer particles wherein said modified first polymer particlesand said second polymer particles have a charge difference of less than20 mV.
 11. The polymer dispersion of claim 9 wherein said additive is anaromatic acid or salt.
 12. The polymer dispersion of claim 11 whereinsaid additive is selected from the group consisting of salicylic acid,phthalic acid, benzoic acid and styrene-4-sulfonic acid.
 13. The polymerdispersion of claim 11 wherein said additive is selected from the groupconsisting of 2,3,4,4-tetrahydroxybutanoic acid,1,2,3,4-butanetetracarboxylic acid and polystyrene sulfonic acid.
 14. Amethod of forming a polymer dispersion comprising: providing aconductive polymer dispersion wherein said conductive polymer comprisesa conductive polymer in a bipolaron state; subjecting said conductivepolymer dispersion to high-pressure homogenization thereby convertingsaid conductive polymer into first polymer particles having a positiveZ-potential and second polymer particles having a negative Z-potential.15. The method of forming a polymer dispersion of claim 14 wherein saidconductive polymer is a bipolaron state has an average particle size of100 to 5,000 nm.
 16. The method of forming a polymer dispersion of claim14 wherein said first polymer particles have a charge of 10 mV to +150mV and said second polymer particles have a charge of 0 mV to −150 mV.17. The method of forming a polymer dispersion of claim 14 wherein saidfirst polymer particles and said second polymer particles have a chargedifference of at least 20 mV.
 18. The method of forming a polymerdispersion of claim 14 wherein said first polymer particles and saidsecond polymer particles have an average particle size of at least 5 nm.19. The method of forming a polymer dispersion of claim 18 wherein saidfirst polymer particles and said second polymer particles have anaverage particle size of at least 10 nm.
 20. The method of forming apolymer dispersion of claim 19 wherein said first polymer particles andsaid second polymer particles have an average particle size of at least50 nm.
 21. The method of forming a polymer dispersion of claim 20wherein said first polymer particles and said second polymer particleshave an average particle size of 100-500 nm.
 22. The method of forming apolymer dispersion of claim 21 wherein said first polymer particles andsaid second polymer particles have an average particle size of 100-200nm.
 23. The method of forming a polymer dispersion of claim 14 furthercomprising an additive wherein said additive adheres to said firstpolymer particles thereby forming an adjunct dispersion.
 24. The methodof forming a polymer dispersion of claim 23 wherein said adjunctdispersion comprises modified first polymer particles wherein saidmodified first polymer particles and said second particles have a chargedifference of less than 20 mV.
 25. The method of forming a polymerdispersion of claim 23 wherein said additive is an aromatic acid orsalt.
 26. The method of forming a polymer dispersion of claim 25 whereinsaid additive is selected from the group consisting of salicylic acid,phthalic acid, benzoic acid and styrene-4-sulfonic acid.
 27. The methodof forming a polymer dispersion of claim 25 wherein said additive isselected from the group consisting of 2,3,4,4-tetrahydroxybutanoic acid,1,2,3,4-butanetetracarboxylic acid and polystyrene sulfonic acid.
 28. Amethod for forming a capacitor comprising: forming an anode; forming adielectric on said anode; forming a conductive polymer layer on saiddielectric by applying a dispersion comprising first polymer particleshaving a positive Z-potential and second polymer particles having anegative Z-potential.
 29. The method for forming a capacitor of claim 28wherein said first polymer particles have a charge of 10 mV to +150 mVand said second polymer particles have a charge of 0 mV to −150 mV. 30.The method for forming a capacitor of claim 28 wherein said firstpolymer particles and said second polymer particles have a chargedifference of at least
 31. The method for forming a capacitor of claim28 wherein said first polymer particles and said second polymerparticles have an average particle size of at least 5 nm.
 32. The methodfor forming a capacitor of claim 31 wherein said first polymer particlesand said second polymer particles have an average particle size of atleast 10 nm.
 33. The method for forming a capacitor of claim 32 whereinsaid first polymer particles and said second polymer particles have anaverage particle size of at least 50 nm.
 34. The method for forming acapacitor of claim 33 wherein said first polymer particles and saidsecond polymer particles have an average particle size of 100-500 nm.35. The method for forming a capacitor of claim 34 wherein said firstpolymer particles and said second polymer particles have an averageparticle size of 100-200 nm.
 36. The method for forming a capacitor ofclaim 28 further comprising an additive wherein said additive adheres tosaid first polymer particles thereby forming an adjunct dispersion. 37.The method for forming a capacitor of claim 36 wherein said adjunctdispersion comprises modified first polymer particles wherein saidmodified first polymer particles and said second particles have a chargedifference of less than 20 mV.
 38. The method for forming a capacitor ofclaim 36 wherein said additive is an aromatic acid or salt.
 39. Themethod for forming a capacitor of claim 38 wherein said additive isselected from the group consisting of salicylic acid, phthalic acid,benzoic acid and styrene-4-sulfonic acid.
 40. The method for forming acapacitor of claim 38 wherein said additive is selected from the groupconsisting of 2,3,4,4-tetrahydroxybutanoic acid,1,2,3,4-butanetetracarboxylic acid and polystyrene sulfonic acid.
 41. Acapacitor comprising: an anode, a dielectric on said anode; and aconductive polymer layer on said dielectric wherein said conductivepolymer layer comprises first polymer particles having a positiveZ-potential and second polymer particles having a negative Z-potential.42. The capacitor of claim 41 wherein said first polymer particles havea charge of 10 mV to +150 mV and said second polymer particles have acharge of 0 mV to −150 mV.
 43. The capacitor of claim 41 wherein saidfirst polymer particles and said second polymer particles have a chargedifference of at least 20 mV.
 44. The capacitor of claim 41 wherein saidfirst polymer particles and said second polymer particles have anaverage particle size of at least 5 nm.
 45. The capacitor of claim 44wherein said first polymer particles and said second polymer particleshave an average particle size of at least 10 nm.
 46. The capacitor ofclaim 45 wherein said first polymer particles and said second polymerparticles have an average particle size of at least 50 nm.
 47. Thecapacitor of claim 46 wherein said first polymer particles and saidsecond polymer particles have an average particle size of 100-500 nm.48. The capacitor of claim 47 wherein said first polymer particles andsaid second polymer particles have an average particle size of 100-200nm.
 49. The capacitor of claim 41 further comprising an additive whereinsaid additive adheres to said first polymer particles thereby forming anadjunct dispersion.
 50. The capacitor of claim 49 wherein said adjunctdispersion comprises modified first polymer particles wherein saidmodified first polymer particles and said second particles have a chargedifference of less than 20 mV.
 51. The capacitor of claim 49 whereinsaid additive is an aromatic acid or salt.
 52. The capacitor of claim 51wherein said additive is selected from the group consisting of salicylicacid, phthalic acid, benzoic acid and styrene-4-sulfonic acid.
 53. Thecapacitor of claim 51 wherein said additive is selected from the groupconsisting of 2,3,4,4-tetrahydroxybutanoic acid,1,2,3,4-butanetetracarboxylic acid and polystyrene sulfonic acid. 54.The capacitor of claim 41 having a working voltage of up to 500 V. 55.The capacitor of claim 54 having a working voltage of 35 V to 500 V. 56.The capacitor of claim 54 having a working voltage of 3 V to 35 V.